How does light affect workers’ health?

Light is not only an essential energy source for life on Earth, but it also greatly affects the human body. It not only allows us to see our surroundings but also stimulates and leads to changes in our mood and activity levels. The amount of light received each day significantly impacts a person’s emotions and physical well-being.

The presence of light in the work environment is a very important factor; a good and optimized lighting system will provide a bright working environment, enhancing spirit, concentration, and work performance. Conversely, a working environment lacking natural light or insufficient illumination according to issued regulations can cause fatigue, stress, and a decline in the worker’s ability to perform.

Besides psychological effects, light also plays a crucial role in regulating the human biological rhythm. Our natural biological clock is primarily regulated by sunlight, helping to regulate sleep, digestion, and growth processes. Working in an environment lacking natural light can lead to visual disturbances, emotional instability, insomnia, etc.

1. What is Light?

Light is a beam of photons from various radiations with wavelengths from 380 – 760nm (Violet – Red) that our eyes can see, and it propagates through space as an electromagnetic wave at a very high speed.

In production labor, the use and regulation of light have significant importance in many areas: occupational hygiene, occupational safety, and economics. Appropriate lighting leads to higher productivity, better product quality, and better health.

Light sources include natural, artificial, and mixed sources.

• Natural light is the direct light from the sun.
• Artificial light is light produced by humans.
• Mixed light is a combination of natural and artificial light.

Some concepts of lighting:

• General lighting or overall lighting is illumination for an entire area or workspace.
• Local lighting is lighting focused on a specific point.
• Mixed lighting is a combination of general and local lighting.
• Shadowing is the phenomenon where the light source reaching the eye is partially obscured.

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2. Where does Light originate within a Manufacturing Plant?

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3. Occupations where Light Poses a Hazard to Workers

Light poses a health risk to workers when the illumination in the work environment does not meet the requirements of the National Technical Regulation on Lighting – Permissible Levels of Illumination in the Workplace, QCVN 22:2016/BYT. There are several occupations where the light factor can be hazardous to workers’ health, such as:

• During welding , the use of strong light sources such as infrared and ultraviolet radiation can cause burns and damage to the eyes and skin. Additionally, the glare from the welding process can cause eye strain and reduce visual clarity.
• Photographers and printing staff are exposed to strong light from flash lamps, photocopiers, laser printers, etc.
• In the production and inspection of electronic components with small details, workers often have to work continuously with local lighting.
• Metal processing , using tools like cutting machines, grinding machines, welding machines, etc., can generate glare and UV radiation harmful to the eyes and skin.
• In the metallurgical industry , workers are exposed to intense light from furnaces, which can cause glare and burns if safety measures are not ensured during work.

For these occupations, applying personal protective measures such as clothing, hats, protective glasses, etc., and safety procedures is very important to protect workers’ health from the negative effects of light.

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4. How Light Affects Worker Comfort

Light has a profound impact on worker comfort in the workplace. Here are some ways light affects worker comfort:

• Natural light and light equivalent to natural light can create a more energized working environment, promoting comfort and better concentration for workers.
• Appropriate lighting helps improve visual acuity, reducing eye fatigue, which allows workers to perform more efficiently, reduce errors, and increase job productivity.
• Light levels can influence human mood and emotions; it can give us feelings of happiness and calmness but can also cause feelings of pessimism and sadness.

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5. Permissible Safe Light Levels in a Manufacturing Plant

According to QCVN 22:2016/BYT National Technical Regulation on Lighting – Permissible Levels of Illumination in the Workplace

Table of minimum maintained illuminance requirements for various rooms, workspaces, and activities:

Type of Room, Work, or Activity	Em (Lux)
1. General Indoor Areas
Entrance Hall	100
Waiting Room	200
Circulation Areas and Corridors	100
Stairs (Elevators, Stairs), Escalators	150
Canteen	150
Rest Room	100
Gym/Fitness Room	300
Locker Room, Washroom, Shower Room, Toilet	200
Patient Room	500
Medical Room	500
Electrical Cabinet Room	200
Mail Room, Switchboard	500
Warehouse, Cold Storage	100
Shipping/Packing Area	300
Conveyors	150
Storage Racks Area	150
Inspection Area	150
2. Industrial and Craft Activities
2.1. Iron and Steel Industry
Production Machinery requiring no manual operation	50
Production Machinery sometimes requiring manual operation	150
Production Area requiring frequent manual operation	200
Steel Warehouse	50
Melting Furnace	200
Rolling, Coiling, Steel Cutting Machines	300
Control Platforms and Control Panels	300
Testing, Measurement, and Inspection	500
Underfloor Tunnels, Conveyors, Silos	50
2.2. Foundries and Metal Casting Enterprises
Underfloor Tunnels, Silos	50
Operating Floor	100
Sand Preparation	200
Fettling (Removing Flashes/Burrs)	200
Working Floor at Furnace and Mixing Stations	200
Mould Making Workshop	200
Mould Knock-out Area	200
Machine Casting	200
Hand Pouring and Core Making	300
Die Casting	300
Pattern Shop	500
2.3. Mechanical Engineering and Manufacturing Industry
Removing Die Blanks	200
Forging, Welding, Benchwork	300
Rough and Medium Precision Machining: Tolerance $\geq 0.1 \text{ mm}$	300
Fine Precision Machining: Tolerance $< 0.1 \text{ mm}$	500
Marking Out, Inspection	750
Wire Drawing, Tube Making (Cold) Workshop	300
Processing Disks Thickness $\geq 5 \text{ mm}$	200
Processing Steel Plates Thickness $< 5 \text{ mm}$	300
Manufacturing Tools, Cutting Equipment	750
Component Assembly:
– Rough	200
– Medium	300
– Fine	500
– Precision	750
Electroplating	300
Surface Treatment and Painting	750
Manufacturing Tools, Molds, Jigs, Precision and Micro-mechanics	1000
2.4. Automotive Manufacturing and Repair Industry
Body Work and Assembly	500
Painting, Spray Booth, Polishing Booth	750
Painting: Repair, Inspection	1000
Seat Production	1000
Final Inspection	1000
Automobile Service, Repair, Inspection	300
2.5. Power Plants
Fuel Supply Station	50
Boiler Workshop	100
Machine Room	200
Auxiliary Rooms, Pump Room, Condensing Room, Switchboard	200
Control Room	500
2.6. Electrical Industry
Cable and Wire Production	300
Coil Winding:
– Large Coils	300
– Medium Coils	500
– Small Coils	750
Insulation Dipping	300
Electroplating	300
Assembly Work:
– Rough Details; e.g., large transformers	300
– Medium Details; e.g., switchboards	500
– Small Details; e.g., telephones, radios, information technology products (computers)	750
– Precision; e.g., measuring instruments, printed circuit boards	1000
Electronics Workshop, Testing, Calibration	1500
2.7. Cement, Concrete, Brick Industry
Material Drying	50
Material Preparation, Work at Mixer, Kiln	200
Machine Operation	300
Rough Mould Making	300
2.8. Ceramics, Glass, Roofing Tile Industry
Material Drying	50
Preparation, Machine Operation	300
Glazing, Rolling, Pressing, Shaping Simple Parts, Glazing, Glass Blowing	300
Grinding, Engraving, Polishing Glass, Shaping Precision Parts, Manufacturing Glass Instruments	750
Grinding Optical Glass, Hand Grinding and Engraving Crystal	750
Precision Work; e.g., grinding, painting, decoration…	1000
Manufacturing Artificial Gemstones	1500
2.9. Chemical, Plastics, and Rubber Industry
Installation of Remotely Controlled Production Processes	50
Installation of Production Processes with Manual Operation	150
Steady Work in Production Processes	300
Precision Measurement Room, Laboratory	500
Pharmaceutical Production	500
Tire Production	500
Color Inspection	1000
Cutting, Repair, Inspection	750
2.10. Paper Industry
Debarking, Pulp Mill	200
Paper Production, Folding Machine, Cardboard Production	300
Bookbinding Work; e.g., folding, collating, gluing, trimming, covering, stitching	500
2.11. Printing Industry
Paper Cutting, Gold Plating, Embossing, Plate Making, Work on Stone and Printing Plate, Printing Press, Matrix Making	500
Paper Sorting and Hand Printing	500
Typesetting, Proofreading, Lithography	1000
Color Inspection in Multi-color Printing	1500
Engraving Steel and Copper Plates	2000
2.12. Leather Industry
Soaking Pits, Drums, Hide Storage Pits	200
Filtering, Shaving, Buffing, Fleshing Hides	300
Saddle Making, Shoemaking, Stitching, Sewing, Polishing, Shaping, Cutting, Stamping	500
Sorting	500
Dyeing Leather (Dyeing Machine)	500
Quality Inspection	1000
Color Inspection	1000
Shoe Making	500
Glove Making	500
2.13. Textile Industry
Working Positions and Cotton Bale Unloading Area	200
Carding, Washing, Ironing, Cotton Tearing Machine, Spinning, Splicing Raw Fiber, Sizing Yarn, Cutting, Twisting Raw Fiber, Twisting Jute and Hemp Fiber	300
Spinning Frame, Winding, Warping, Weaving, Braiding, Knitting	500
Sewing, Fine Knitting, Embroidery	750
Hand Designing, Pattern Drawing	750
Finishing, Dyeing	500
Drying Room	100
Automatic Fabric Printing	500
Mending Snags, Adjustments	1000
Color Inspection, Fabric Inspection	1000
Defect Repair	1500
Hat Making	500
2.14. Wood Products Manufacturing Industry
Automatic Process; e.g., drying, plywood production	50
Steaming Chamber	150
Sawmill	300
Workbench Operations, Gluing, Assembly	300
Polishing, Painting, Fine Joinery	750
Work on Woodworking Machines; e.g., planing, routing, carving, grooving, cutting, sawing, chiseling, drilling	500
Veneer Selection, Marquetry, Carving, Inlay	750
Quality Inspection	1000
2.15. Food Industry
Working Positions and Areas in:
– Breweries, Malt Houses	200
– Washing, Bottling, Cleaning, Sieving, Peeling	200
– Cooking Area in Jam and Chocolate Factories	200
– Working Areas and Confined Spaces in Sugar Factories	200
– Drying, Curing Raw Tobacco, Fermentation	200
Sorting and Washing Products, Grinding, Mixing, Packaging	300
Working Areas and Confined Spaces in Slaughterhouses, Butcher Shops, Dairy Factories, on Sifting Floors, at Sugar Refineries	500
Cutting and Sorting Vegetables and Fruits	300
Ready-to-eat Food Processing, Kitchen Work	500
Cigar and Cigarette Production	500
Glass and Bottle Inspection, Product Inspection, Adjustment, Decoration	500
Laboratory	500
Color Inspection	1000
2.16. Baking
Preparation and Baking	300
Finishing, Boxing, Decoration	500
2.17. Agriculture
Loading and Unloading Goods, Operating Equipment and Machinery	200
Livestock Housing	50
Sick Animal Pens, Birthing Pens	200
Feed Preparation, Dairy Storage and Production Area, Equipment Washing	200
2.18. Jewelry Making
Gemstone Processing	1500
Jewelry Manufacturing	1000
Watchmaking (Handmade)	1500
Watchmaking (Automatic)	500
2.19. Hairdressing Salon
Hair Styling	500
2.20. Laundry and Dry Cleaning
Receiving Goods, Marking and Sorting	300
Washing and Dry Cleaning	300
Ironing, Pressing	300
Inspection and Adjustment	750
2.21. Retail Stores
Sales Area	300
Cash Desk Area	500
Packaging Desk	500
2.22. Offices, Public Administration
General Work Rooms, Filing, Photocopying	300
Typing, Data Processing Room	500
Technical Drawing Room	750
Computer Design	500
Meeting, Conference Room	300
Reception Desk	300
Storage Room	200
3. Public Areas
3.1. General Areas
Entrance, Lobby	100
Cloakroom	200
Waiting Room	200
Ticket Office	300
3.2. Restaurants, Hotels
Reception Desk, Cashier, Luggage Check-in Desk	300
Kitchen	300
Restaurant, Dining Room, Function Room	200
Self-Service Restaurant	200
Buffets	300
Meeting Room	300
Corridor	100
3.3. Theatres, Concert Halls, Cinemas
Rehearsal Room, Changing Room	300
Maintenance, Cleaning of Seating Area	200
Stage Construction, Assembly	300
3.4. Trade Fairs, Exhibition Halls
General Lighting	300
3.5. Libraries
Book Stacks	200
Reading Room	500
Cashier, Book Circulation Desk	300
3.6. Public Parking Garages (Indoor)
Ramps In/Out (Daytime)	300
Ramps In/Out (Nighttime)	75
Traffic Lanes	75
Parking Area	75
Ticket Booth	300
4. Schools
4.1. Daycare, Kindergarten
Playroom	300
Childcare Room	300
Craft Room	300
4.2. Schools
Lecture Halls, Classrooms, Study Rooms	300
Blackboard, Green Wall Board, Whiteboard	500
Demonstration Table	500
Art Room	500
Art Room in Art Schools	750
Technical Drawing Room	750
Practical and Laboratory Rooms	500
Vocational Workshop, Craft Room	500
Music Practice Room	300
Computer Practice Room	300
Preparation Room and Experimental Workshop	300
Circulation Areas, Corridors	100
Stairs	150
Common Student Room and School Council Meeting Room	200
Teacher’s Room	300
Library: Book Stacks	200
Library: Reading Room	500
Storage Room for Teaching Tools	100
Sports Hall, Gymnasium, Swimming Pool (General Use)	300
School Canteen	150
Kitchen	300
5. Healthcare Facilities
5.1. Common Use Rooms
Corridor: Daytime	100
Corridor: Cleaning	100
Corridor: Nighttime	50
Corridor: Multi-purpose Use	200
Passenger Elevator	100
Service Elevator (Transfer of Machinery, Equipment, Tools)	200
Waiting Room	200
On-Call Room	200
Patient Bathroom and Toilet	200
5.2. Staff Rooms
Administrative Room	300
Staff Room	300
5.3. Maternity Clinic
General Lighting	300